Member Site Core: Publicly-funded cancer clinical trials continue to establish new standards of care and improve outcomes for cancer patients. ECOG-ACRIN (EA) has instituted an organizational matrix based on the integration of biological and imaging studies with clinical trials of novel anti-cancer therapies to conduct cutting-edge clinical research and promote scientific discovery. We have incorporated expertise in imaging, cancer biology and therapy within our scientific organization, working closely with the biostatistics and data management centers at the Dana Farber Cancer Institute and Brown University, to propose a research plan that recognizes the importance of biomarkers to bring precisely targeted clinical trials to broad populations of cancer patients. The EA biorepositories, image databases, immunological laboratories, and associated translational science centers will bring together the correlative science studies that relate cancer biology to clinical markers of treatment effect in a data-rich environment. EA embraces the goals and spirit of the NCTN to conduct science-driven clinical trials to improve the lives of adults with cancer. EA clinical trials are implemented through an efficient operational infrastructure that enables access to cutting-edge treatments across the US from large cancer centers to community practices and assures accrual to complex trials in cancers of varying prevalence. Our science is driven by our membership, which includes the NCI-funded Cancer Centers, the Specialized Programs of Research Excellence (SPOREs), the ETCTN (Experimental Therapeutics Clinical Trials Network), the Quantitative Imaging Network (QIN), the NCTN Lead Academic Participating Sites (LAPS), and the National Community Oncology Research Programs (NCORP). As committed participants in the NCTN and in all aspects of CTEP-led cancer research, EA collaborates across the system to promote and advance the collective efforts of all of the groups. We make available the mentorship and opportunity needed to nourish the next generation of investigators. EA is positioned to make unique contributions to the NCTN, working to translate NCI-supported science into improved outcomes for cancer patients. This model, together with developing innovation in large data analysis, will yield high quality trials that have the potential to be practice-changing, applicable to both academic and community environments, and providing imaging and other biomarkers to identify patients who benefit most. In the Member Site Core, we describe how our various member categories come together to comprise EA, how we maintain this roster, and what requirements define continued membership. We credential the sites, monitor the extent and quality of their activities, and assess their overall contributions relative to peers in the same categories at an elaborate annual review, the Institutional Evaluation. Accrual of special populations is a priority, but even more, as discussed in the Overall section, is a key scientific theme of EA, with important implications for cancer care in the community at large. Rare cancers, however defined, are addressed in all of the disease committees, as well as in science committees, including Developmental Therapeutics.